Adaptive braking modulator

ABSTRACT

An adaptive braking system for an automotive vehicle is disclosed which permits the proportioning unit valve commonly used in vehicle braking systems to also function as the adaptive braking modulator. The device provides a fluid motor which engages the proportioning piston and urges the latter into sealing engagement with the poppet member to prevent fluid communication to the brakes of the vehicle when an adaptive braking cycle has initiated. Thereafter, the fluid motor continues to urge the proportioning piston in a direction enlargening the outlet chamber of the proportioning valve, to thereby reduce the fluid pressure level communicated to the vehicle brakes. An electrically actuated solenoid valve is responsive to an output signal from an electronic control unit when an adaptive braking cycle is initiated to communicate fluid pressure to the fluid motor for operating the latter.

Mai. 5 1974 1 ADAPTHVE BRAKING MODULATOR [75] Inventors: Martin A.Shields; David A.

Jackson, both of South Bend, 1nd.

Assignee: The Bendix Corporation, South Bend, Ind. v

Filed: Sept. 18, 1972 Appl. No.: 289,930

US. Cl 303/6 C, 303/21 F Int. Cl B60t 8/12 Field of Search 303/6, 21,61-63, 303/68-69, 10,,84 R, 13, 15; 188/181, 349, 152, 151 A; 91/4343,515,440 6/1970 Every et a1. 3,567,290 3/1971 Liggett et al 303/6 CPrimary ExaminerDuane A. Reger Assistant ExaminerD. C. Butler Attorney,Agent, or FirmKen C.- Decker; William N. Antonis 57 ABSTRACT An adaptivebraking system for an automotive vehicle is disclosed which permits theproportioning unit valve commonly used in vehicle braking systems toalso function as the adaptive braking modulator. The device provides afluid motor which engages the proportioning piston and urges the latterinto sealing engagement with the poppet member to prevent fluidcommunication to the brakes of the vehicle when an adaptive brakingcycle has initiated. Thereafter, the fluid motor continues to urge theproportioning piston in a direction enlargening the outlet chamber ofthe proportioning valve, to thereby reduce the fluid pressure levelcommunicated to the vehicle brakes. An electrically actuated solenoidvalve is responsive to an output signal from an electronic control unitwhen an adaptive braking cycle is initiated to communicate fluidpressure to the fluid motor for operating the latter.

5 Claims, 3 Drawing Figures PATENTEB "AR 51974 SHEET 1 OF 2 1 ADAPTIVEBRAKING MODULATOR BACKGROUND OF THE INVENTION This invention relates toa modulator for use in an automotive adaptive braking system.

A modulator is necessary in an automotive adaptive braking system tocontrol the fluid communication to the controlled brakes of the vehicleto prevent skidding of the latter. Heretofore, most adaptive brakingmodulators have been rather sophisticated designs and have consequentlybecome quite expensive to manufacture. For this reason, adaptive brakingsystems have not found wide acceptance in the automotive industry. Also,many vehicle braking systems are provided wtih a proportioning valvewhich reduces braking pressure communicated to the rear wheel brakes tomake them compatible with the front wheel brakes. These proportioningvalves have been widely used for a number of years and consequentlymaybe manufactured at a relatively low cost. The present inventionproposes using the proportioning valve as a part of the adaptive brakingmodulator, so that the cost of the latter may be reduced.

- SUMMARY OF THE INVENTION Therefore, an important object of'ou'rinvention is to substantially reduce the cost of an adaptive brakingmodulator.

Another important object of our invention is to enable the conventionalbrake proportioning valve used in many existing brake systems to alsofunction as an adaptive braking modulator.

Stillanother important object of our invention is to provide adifferential pressure operated fluid motor for controlling actuation ofa proportioning valve. so that the latter may be used as an adaptivebraking modulator.

A still further object of our invention is to provide a brakeproportioning valve used in existing braking systems with a differentialfluid pressure motor for operating the latter and also to provide anelectrically a'ctuated valve that is responsive to the output signal ofan electronic control unit for communicating a pressure differentialacross the fluid motor.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration ofabraking system made pursuant to the teachings of our present inventionwith the fluid motor actuated proportioning valve used thereinillustrated in cross section;

FIG. 2 is a cross-sectional view taken substantially alonglines 22 ofFIG. 1;

FIG. 3 is an illustration similar to FIG. I, but illustrating anotherembodiment of our invention.

DETAILED DESCRIPTION Referring now to the drawings, a combination brakeproportioning valve and adaptive braking modulator generally indicatedby the numeral 10 includes a housing 12 having an inlet port 14 and anoutlet port 16. The outlet port I6 is communicated to the rear wheelbrakes 18 of the vehicle. The inlet port 14 is communicated to one sideof a conventional automotive split system master cylinder 20 whichdevelops hydraulic pressure in the braking system in the conventionalmanner. The other side of the master cylinder 20 is connected to thefront wheel brakes 22 of the vehicle. The master cylinder 20 is actuatedby the vehicle operator by operation of a conventional pedal 24, whichis mounted in the operators compartment of the vehicle. A hydraulicbrake booster 26 is provided which includes a pressure chamber (notshown) which provides a power assist to the vehicle operator inoperation of the master cylinder 20. The hydraulic booster 26 may be ofany conventional design, such as the one disclosed in U. S. Pat. No.3,603,209, owned by the assignee of the present invention andincorporated herein by reference. The booster disclosed in theaforementioned patent utilizes the fluid pressure output of the vehiclepower steering pump 28 to develop hydraulic pressure to provide thepower assist in the pressure chamber of the hydraulic brake booster. Thehydraulic booster 26 is connected in the same hydraulic circuit with thevehicles power steering gear 30 so that the fluid pressure output forthe pump 28 may be used to both actuate the hydraulic brakevbooster 26and the power steering gear 30.

Referring again to the valve 10, the housing 12 defines a bore 32therewithin whichvis divided into an inlet chamber 34 and an outletchamber 36 by valve elements generally indicated by the numeral 38.Valve elements 38 include a proportioning piston 40 which is providedwith an axial passage 42 therewithin which communicates the chamber 34with the chamber 36. The valve piston 40 is stepped to present a largerdiameter end 44 exposed to the fluid pressure level in the chamber 36and a smaller diameter end 46 exposed to the fluid pressure level in thechamber 34. The cavity 48 which is defined between the shoulder 50 onthe proportioning piston 40 and a similar shoulder 52 on the housing 12is vented to the exterior of the housing 12 by a vent passage 54. Theproportioning piston 40 is urged into the position illustrated in FIG.I, with the rightwardmost end of the piston 40 engaged with the end 56of the chamber 36, by a spring 58.

Valve elements 38 further include a poppet member 60 which cooperateswith the axial passage 42 in the proportioning piston 40 to controlfluid communication therethrough, as will be described in detailhereinafter. The poppet member 60 includes an internal recess 62 whichis slidably received upon a support member 64 which forms a part of thehousing 12. A spring 66 urges the abutment 68 on the poppet member 60into engagement with a corresponding abutment 70 on a retainer member 72carried in the bore 32, so that movement of the poppet member 60 to theright is limited, but movement ofthe poppet member 60 to the leftviewing FIG. 1 is permitted.

The valve 10 is operated during an adaptive braking cycle by a fluidmotor generally indicated by the numeral 74. The fluid motor 74 includesa piston 76 slidably mounted in a bore 78 defined within the housing l2.A rod 80 extends from the piston 76 and projects through the end 56 ofthe chamber 36 to engage the end 44 of the proportioning piston 40. Thefluid motor 74 is actuated by communicating fluid pressure into achamber 82 defined between the right hand end of the piston 76 (viewingFIG. 1) and the end of the bore 78. Fluid communication into the chamber82 for actuating the piston 76 is controlled by an electrically actuatedvalve generally indicated by the numeral 84. The valve 84 includesaninlet port 86. which is communicated to the high pressure fluid at theinlet of the brake booster 26 through a conduit 87 so that the port 86is always supplied with high pressure fluid whenever the brake booster26 is actuated. The valve 84 further includes an outlet or return port88 which is communicated to a reservoir (not shown) at the inlet or lowpressure side of the power steering pump 28 through the conduit 90. Thecontrol valve 84 further includes a pair of opposed valve seats 92, 94.The valve element 96 is disposed between the seats 92 and 94, and aspring 98 and a plunger 100 normally cooperate to urge the valve element96 into sealing engagement with the valve seat 92 and away from thevalve seat 94 to permit the chamber 82 to communicate with the lowpressure side of the pump 28 and to prevent communication of highpressure fluid from the port 86 into the chamber 82. An electricallyactuated solenoid generally indicated by the numeral 102 includes anarmature 104 which is movable toward and away from a magnetic pole piece106 which is integral with the valve seat 92. Solenoid 102 furtherincludes a coil 108, and when current is passed through the coil 108,the armature 104 is urged toward the pole piece 106 through the air gapA in a manner well known to those skilled in the art. A rod 109transmits movement of the armature 104 to the valve element 96, so thatwhen the solenoid 102 is actuated. the valve element 96 is urged fromthe valve seat 92 into sealing engagement with the valve seat 94, tothereby terminate fluid communication between the chamber 82 and theport 88 and to permit high pressure fluid communicated from the port 86into the chamber 82. The solenoid 108 is actuated by an electroniccontrol unit 110 which is responsive to the speed of either of thewheels controlled by the rear wheel brake 18. A speed sensor indicatedschematically at 112 senses the speed of the rear wheel, and transmitsan appropriate signal to the control unit 110. The control unit 110contains appropriate logic which responds to the speed of the rearwheels 18 to generate a control signal actuating the solenoid 102 whenan incipient skidding condition is sensed. Logic contained in thecontrol unit 110 may be made pursuant to any of a number of designs.such as that disclosed in copending U. S. Patent application Ser. No.227.748 filed Feb. 22, 1972, owned by the assignee of the presentinvention and incorporated herein by reference.

MODE OF OPERATION Various components of valve are illustrated in FIGS. 1and 2 in the positions which they assume when the brakes of the vehicleare released. When the vehicle operator initiates a brake applicationwhich does not require an adaptive braking cycle, fluid pressuredeveloped in the master cylinder is communicated into the chamber 34 andis immediately communicated to the rear wheel brakes 18 ofthe vehiclefor actuating the latter through the axial passage 42 and the outletchamber 36. However. since the end 44 of the piston 40 has a muchgreater area against which fluid pressure in the outlet chamber 36 mayreact than does the end 46 of the piston 40 exposed to the fluidpressure level in the chamber 34, at a relatively low pressure level theforce differential created across the valve piston 40 due to thesedifferential areas will overcome the force of the spring 58 to urge thevalve proportioning piston 40 into sealing engagement with the poppetmember 60 to thereby terminate further fluid communication through thepassage 42. However, if the fluid pressure level in the inlet chamber 34is increased, the valve will, of

course, reopen to permit fluid to communicate into the outlet chamber36; however, because of the differential areas across the valve piston40, only a fraction of the fluid pressure increase in the chamber 34will be communicated into the outlet chamber 36. Therefore, the fluidpressure level in outlet chamber 36 is less than the fluid pressurelevel in the inlet chamber 34 by a predetermined ratio. Further detailsof the construction and operation of the valve element 38, includingtheir operation when the brakes of the vehicle are released, are morecompletely described in U. S. Pat. No. 3,556,607 owned by the assigneeof the present invention and incorporated herein by reference.

When the electronic control unit 110 senses an incipient skiddingcondition of the wheel controlled by the brakes 18, the control unit 110transmits a signal actuating the solenoid valve 102 to urge the valveelement 96 into a position terminating fluid communication between thechamber 82 and the inlet of the pump 28 and initiating fluidcommunication between the high pressure fluid at the inlet port 86 andthe chamber 82. High pressure fluid in the chamber 82 acts upon the endof the piston 76 to urge the latter to the left viewing FIG. 1, therebydriving the end of rod into engagement with the end of the piston 40 andthereafter driving the piston 40 into sealing engagement with the poppetmember 60 to thereby terminate fluid communication to the axial passage42 to shut off fluid communication between the brakes 18 and the mastercylinder 20 to thereby prevent a further buildup of fluid pressure inthe brakes 18 which might cause the wheels controlled by the latter toskid. Further movement ofthe piston 76 urges the piston 40 away from theclosed end 56 of the chamber 36, to thereby expand the volume of theoutlet chamber 36. As the volume of the outlet chamber 36 expands, thepressure level in the brakes 18 is reduced. thereby relieving the latterand permitting the .wheels controlled by the brakes 18 to spin up orreaccelerate so that they are no longer in danger of locking. When thisoccurs. the electronic control unit terminates operation of the solenoid102 to permit the spring 98 and plunger 100 to urge the valve element 96away from the valve seat 94 and back into engagement with the valve seat92'to thereby terminate communication of high pressure fluid into thechamber 82 and to vent the latter to the low pressure side of the powersteering pump 28, When this occurs, the spring 58, and pressure inchamber 34 acting on end 46 of piston 40 urges the valve piston 40 andthe piston 76 to the right viewing FIG. 1, to thereby reestablish fluidcommunication through the axial passage 42 to the rear wheel brakes 18.

DETAILED DESCRIPTION OF THE ALTERNATE EMBODIMENT In the embodiment ofFIG. 3, elements the same as those in the embodiments of FIGS. 1 and 2retain the same reference numerals. The embodiment of FIG. 3 isidentical to the embodiment of FIGS. 1 and 2, except that the highpressure fluid motor 74 in the embodiments of FIGS. 1 and 2 is replacedby a vacuumoperated fluid motor generally indicated by the numeral 114in FIG. 3. A diaphragm 116 is mounted within a pressure can 118 anddivides the latter into chambers 120 and 122. A vent 124 vents thechamber 120 to atmosphere at all times. A three-way solenoidactuatedvalve 126, which is substantially the same as the valve 84 illustratedin FIG. 1, controls communication into the chamber 122. Three-waysolenoid valve 126 is actuable from a first position terminating fluidcommunication between the chamber 122 and a vacuum source (not shown)and permitting the fluid communication from the atmosphere into thechamber 122, to a second position actuating the chamber 122 fromatmosphere and communicating a vacuum from the vacuum source (which maybe, for example, the manifold vacuum of the vehicle engine) into thechamber 122. When the chamber 122 is communicated with a vacuum source,the high pressure atmospheric air in the chamber 120 urges the diaphragm116 to the left viewingFlG. 3, so that the rod 80 is urged intoengagement with the valve proportioning piston 40. Further movementof'the diaphragm 116 actuates the valve piston 40 in a manner identicalto that described in connection with the preferred embodiment discussedhereinabove. A spring 125 is provided to urge the dia phragm 116 back toits normal position when the adaptive braking cycle is terminated andair at atmospheric pressure is again communicated into the chamher 122.Of course it will be obvious to those skilled in the art thatalternatively both sides of the diaphragm 116 may be initiallycommunicated to the vacuum source and that chamber 122 be communicatedto atmosphere when the adaptive braking cycle is initiated.

We claim: 1. In a braking system for a wheeled vehicle having a fluidpressure actuated brake controlling one of the wheels of the vehicle:

operator-operated pressure developing means for developing brakingpressure for actuating said brake;

proportioning valve means having an inlet communicated to said pressuredeveloping means and an outlet communicated to said brake, saidproportioning valve means permitting uninhibited fluid communicationbetween said inlet and outlet until a first fluid pressure level isattained at said inlet whereupon said proportioning valve meansproportions fluid communication from said inlet to said outlet toestablish a lower fluid pressure level at said outlet than at saidinlet;

control means responsive to an incipient skidding condition of the wheelcontrolled by said brake and generating an output signal in response tosaid incipient skidding condition; and

electrically actuated means responsive to said control signal forclosing said valve means to prevent fluid communication from said inletto said outlet upon generation of said control signal,

said electrically actuated means including a fluid motor having apressure differential responsive piston operatively associated with saidproportioning valve means, and electrically actuated valve meansresponsive to said control signal to communicate a pressure differentialacross said piston, whereupon said piston moves to close saidproportioning valve means;

said electrically actuated valve means communicating one side of saidpiston with a source of vacuum when said control signal is generated,whereupon atmospheric pressure acting on the other side of said pistonactuates the latter.

2. in a braking system for a wheeled vehicle having a fluid pressureactuated brake controlling one of the wheels of the vehicle;

operator-operated pressure developing means for developing brakingpressure for actuating said brake;

proportioning valve means having an inlet communi cated to said pressuredeveloping means and an outlet communicated to said brake, saidproportioning valve means permitting uninhibited fluid communicationbetween said inlet and outlet until a first fluid pressure level isattained at said inlet whereupon said proportioning valve meansproportions fluid communication from said inlet to said outlet toestablish a lower fluid pressure level at said outlet than at saidinlet;

control means responsive to an incipient skidding condition of the wheelcontrolled by said brake and generating an output signal in response tosaid incipient skidding condition; and

electrically actuated means responsive to said control signal forclosing said valve means to prevent fluid communication from said inletto said outlet upon generation of said control signal;

said electrically actuated means including a fluid motor having apressure differential responsive piston operatively associated with saidproportioning valve means, and electrically actuated valve meansresponsive to said control signal to communicate a pressure differentialacross said piston, whereupon said piston moves to close saidproportioning valve means,

said proportioning valve means including a housing defining a boretherewithin, valve elements dividing said bore into an inlet chambercommunicated to said inlet between said valve elements and one end ofsaid bore and an outlet chamber communicated to said outlet between saidvalve element and the other end of said bore, said valve elements havingto and from sealing engagement with one another to proportion fluidcommunication between said chambers;

said piston moving from a first position permitting said valve elementsto move relative to one another to a second position maintaining saidvalve elements in sealing engagement with one another, further movementof said piston moving one of said valve elements away from said otherend of said bore to increase the volume of said outlet chamber,

whereby the fluid pressure level in the latter communicated to saidbrake is reduced. 3. The invention of claim 2: said housing defining acompartment therewithin between said other end of said bore and the endof said housing, said piston being slidable in said compartment andincluding a rod extending through said other end of the bore forengagement with said one valve element when said piston moves to saidsecond position.

4. In a braking system for a wheeled vehicle having a fluid pressureactuated brake controlling one of the wheels of the vehicle:

operator-operated pressure developing means for developing brakingpressure for actuating said brake;

proportioning valve means having an inlet communicated to said pressuredeveloping means and an outlet communicated to said brake, saidproportioning valve means permitting uninhibited fluid communicationbetween said inlet and outlet until a first fluid pressure level isattained at said inlet whereupon said proportioning valve meansproportions fluid communication from said inlet to said outlet toestablish a lower fluid pressure level at said outlet than at saidinlet;

control means responsive to an incipient skidding condition of the wheelcontrolled by said brake and generating an output signal in response tosaid incipient skidding condition; and

electrically actuated means responsive to said control signal forclosing said valve means to prevent fluid communication from said inletto said outlet upon generation of said control signal;

said proportioning valve means including a housing defining a boretherewithin, valve elements dividing said bore into an inlet chambercommunicated to said inlet port between said valve elements and one endof said bore and an outlet chamber between said valve elements and theother end of said bore communicated to said outlet port, said valveelements moving to and from sealing engagement with one another toproportion fluid communication between said chambers;

said electrically actuated means being effective to maintain said valveelements in sealing engagement with one another and to move said valveelements away from the other end of said bore to increase the volume ofsaid outlet chamber, whereby the fluid pressure level in the lattercommunicated to said brake is reduced.

5. The invention of claim 4:

said electrically actuated means including a plunger extending throughthe other end of said bore, said plunger urging said valve elements intosealing engagement with one another and away from the other end of thebore upon generation of said controlsignal.

1. In a braking system for a wheeled vehicle having a fluid pressureactuated brake controlling one of the wheels of the vehicle:operator-operated pressure developing means for developing brakingpressure for actuating said brake; proportioning valve means having aninlet communicated to said pressure developing means and an outletcommunicated to said brake, said proportioning valve means permittinguninhibited fluid communication between said inlet and outlet until afirst fluid pressure level is attained at said inlet whereupon saidproportioning valve means proportions fluid communication from saidinlet to said outlet to establish a lower fluid pressure level at saidoutlet than at said inlet; control means responsive to an incipientskidding condition of the wheel controlled by said brake and generatingan output signal in response to said incipient skidding condition; andelectrically actuated means responsive to said control signal forclosing said valve means to prevent fluid communication from said inletto said outlet upon generation of said control signal; said electricallyactuated means including a fluid motor having a pressure differentialresponsive piston operatively associated with said proportioning valvemeans, and electrically actuated valve means responsive to said controlsignal to communicate a pressure differential across said piston,whereupon said piston moves to close said proportioning valve means;said electrically actuated valve means communicating one side of saidpiston with a source of vacuum when said control signal is generated,whereupon atmospheric pressure acting on the other side of said pistonactuates the latter.
 2. In a braking system for a wheeled vehicle havinga fluid pressure actuated brake controlling one of the wheels of thevehicle; operator-operated pressure developing means for developingbraking pressure for actuating said brake; proportioning valve meanshaving an inlet communicated to said pressure developing means and anoutlet communicated to said brake, said proportioning valve meanspermitting uninhibited fluid communication between said inlet and outletuntil a first fluid pressure level is attained at said inlet whereuponsaid proportioning valve means proportions fluid communication from saidinlet to said outlet to establish a lower fluid pressure level at saidoutlet than at said inlet; control means responsive to an incipientskidding condition of the wheel controlled by said brake and generatingan output signal in response to said incipient skidding condition; andelectrically actuated means responsive to said control signal forclosing said valve means to prevent fluid communication from said inletto said outlet upon generation of said control signal; said electricallyactuated means including a fluid motor having a pressure differentialresponsive piston operatively associated with said proportioning valvemeans, and electrically actuated valve means responsive to said controlsignal to communicate a pressure differential across said piston,whereupon said piston moves to close said proportioning valve means;said proportioning valve means including a housing defining a boretherewithin, valve elements dividing said bore into an inlet chambercommunicated to said inlet between said valve elements and one end ofsaid bore and an outlet chamber communicated to said outlet between saidvalve element and the other end of said bore; said valve elements havingto and from sealing engagement with one another to proportion fluidcommunication betwEen said chambers; said piston moving from a firstposition permitting said valve elements to move relative to one anotherto a second position maintaining said valve elements in sealingengagement with one another, further movement of said piston moving oneof said valve elements away from said other end of said bore to increasethe volume of said outlet chamber, whereby the fluid pressure level inthe latter communicated to said brake is reduced.
 3. The invention ofclaim 2: said housing defining a compartment therewithin between saidother end of said bore and the end of said housing, said piston beingslidable in said compartment and including a rod extending through saidother end of the bore for engagement with said one valve element whensaid piston moves to said second position.
 4. In a braking system for awheeled vehicle having a fluid pressure actuated brake controlling oneof the wheels of the vehicle: operator-operated pressure developingmeans for developing braking pressure for actuating said brake;proportioning valve means having an inlet communicated to said pressuredeveloping means and an outlet communicated to said brake, saidproportioning valve means permitting uninhibited fluid communicationbetween said inlet and outlet until a first fluid pressure level isattained at said inlet whereupon said proportioning valve meansproportions fluid communication from said inlet to said outlet toestablish a lower fluid pressure level at said outlet than at saidinlet; control means responsive to an incipient skidding condition ofthe wheel controlled by said brake and generating an output signal inresponse to said incipient skidding condition; and electrically actuatedmeans responsive to said control signal for closing said valve means toprevent fluid communication from said inlet to said outlet upongeneration of said control signal; said proportioning valve meansincluding a housing defining a bore therewithin, valve elements dividingsaid bore into an inlet chamber communicated to said inlet port betweensaid valve elements and one end of said bore and an outlet chamberbetween said valve elements and the other end of said bore communicatedto said outlet port, said valve elements moving to and from sealingengagement with one another to proportion fluid communication betweensaid chambers; said electrically actuated means being effective tomaintain said valve elements in sealing engagement with one another andto move said valve elements away from the other end of said bore toincrease the volume of said outlet chamber, whereby the fluid pressurelevel in the latter communicated to said brake is reduced.
 5. Theinvention of claim 4: said electrically actuated means including aplunger extending through the other end of said bore, said plungerurging said valve elements into sealing engagement with one another andaway from the other end of the bore upon generation of said controlsignal.